One gene, one protein, one function - not so

With the abrupt and uninvited introduction of genetically modified (GM) food into our supermarkets and restaurants, many of us are looking more closely into the food we eat.

Recently, Monsanto’s apparent transformation from agrichemical giant to philanthropic institution was cynically trumpeted to the world’s media: “We will double crops yields!” Such grandiose promises can only be offered if there is a parallel narrative that portrays genetic engineering as being able to permit the precise control of life processes and by extension, provide predictable and controllable agricultural outcomes.

Through modern methods found in biotechnology, researchers can accomplish the desired results, but in a more efficient and predictable manner (than in conventional plant breeding). In this process, a specific gene, or blueprint of a trait, is isolated and removed from one organism then relocated into the DNA of another organism to replicate that similar trait (my emphasis).

But are the techniques that give rise to GM foods as precise and controlled as the PR blurb suggests?

First of all, the scientist has to identify a gene that he or she believes will confer a trait to another organism. Using chemical shears, the foreign gene is cut and pasted into a viral “ferry”. Viruses are used because of their unique ability to transfer genetic material across species boundaries, which is usually required in most GM products. To this viral vector are attached controversial “promoter” and “antibiotic-resistant marker” genes.

The entire package is duplicated many times, coated onto microscopic gold and tungsten “bullets” and literally blasted from a gene gun into the Petri dish containing the host cells. The scientist hopes upon hope that the entire package will be neatly inserted into the DNA of a host cell. Most miss their target. Some pass right through without delivering their payload leaving behind damaged DNA. Some cells end up with only portions of the package, some multiple copies. The fact that the DNA of the host organism can withstand such a violent barrage and survive relatively intact, says more of nature’s resilience than the precision of the scientist.

Michael Antoniou, molecular geneticist at King’s College London says of the biolistics process, “It’s the imprecise way in which genes are combined and the unpredictability in how the foreign gene will behave in its new host that results in uncertainty. From a basic genetics perspective, GM possesses an unpredictable component that is far greater than the intended change.”

The biolistics process has direct relevance for Australian consumers. Monsanto’s GM canola being harvested in Victoria for the first time this year, has 40 “rungs” of the parent plant DNA “ladder” (base pairs) missing at one end of the new code insertion. At the other end there are 22 new rungs on the DNA ladder. It is not known where they came from (The EFSA Journal (2004) 29, 1-19).

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It took geneticists more than 270 tries to clone “Dolly” the sheep. But what of the 269 Dollys that didn’t make it? Many were deformed and disfigured, stillborn or unable to mature. Genetic engineering also creates many abnormal plants in the process of obtaining a few that end up being the progenitors of our food plants. Tobacco plants were genetically modified with the intention to increase their natural acid profile. Instead they produced a toxic compound not normally found in tobacco. A genetically modified potato unintentionally increased its starch content some 40 to 200 times.

The biotech industry erroneously believes that their foreign gene will behave exactly as it does in its natural setting. The working assumption is that genes determine characteristics in linear causal chains: one gene, gives one protein, gives one function.

This was the dominant model that held sway in the 1960s and is still a powerful tool for teaching the fundamentals of genetics, but like Einstein’s extension to Newtonian physics, our knowledge of genetics has evolved immeasurably.